This invention relates to water swellable absorbent articles made from crosslinked polyelectrolytes, methods for their preparation, and to a composition consisting of polyelectrolytes containing a copolymerized crosslinker which is useful to make absorbent articles.
It is known from U.S. Pat. Nos. 3,669,103 and 3,670,731 that cross-linked polymeric sorbents can be sandwiched between flexible supports to achieve disposable diapers or dressings.
It is further known from U.S. Pat. Nos. 2,988,539; 3,393,168; 3,514,419 and 3,557,067 that water swellable cross-linked carboxylic copolymers can be prepared. However, these prior art copolymers are all crosslinked during copolymerization or crosslinked after polymerization with subsequent neutralization of the carboxylic acid groups to form water swellable polyelectrolytes and hence these prior art polyelectrolytes cannot be crosslinked in situ as a coating on a substrate or as a flexible film thereof.
It is known from Ser. No. 468,794 filed April 9, 1974, now U.S. Pat. No. 3,980,663, and Ser. No. 450,650 filed March 13, 1974, now U.S. Pat. No. 3,926,891, that water swellable cured articles can be made from polyelectrolytes that have been crosslinked after polymerization with the addition of special crosslinking compounds prior to the heating or curing step.
The present invention is an improvement over these inventions in that the crosslinking agent is built into or copolymerized with polyelectrolytes during polymerization. The advantage of this invention is that only a single solution needs to be sent to users and the chance of operator error in the mixing of the crosslinking agents is eliminated.